Our invention is particularly designed to meet the needs of the shipbuilding industry, in that our robots are adept at climbing the sides of ships' hulls to inspect, clean (including scraping and/or removing of barnacles and ocean scum), paint, and weld them and to perform any other function one may wish to perform on a ship's hull from a readily manipulable, adherent robot, even on a very steep or even backwardly slanted surface. While my invention is particularly good for performing such tasks on ships' hulls, it may be used in any environment requiring such a remotely controlled device, whether or not the surface tends to curve backwardly and upwards. Various approaches have been proposed for accomplishing such tasks. See, for example, Perego's U.S. Pat. No. 3,973,711, describing a magnetic crawler for soldering. It has been known to make and use remotely controlled devices which adhere to a surface by vacuum. See, for example, Lisec's U.S. Pat. No. 4,667,555 disclosing such a device for cutting glass, the more versatile traveling device of Urakami described in U.S. Pat. No. 4,926,957, and Ochiai's U.S. Pat. No. 4,785,902, showing suction cups which can be slightly tilted to maneuver the device which carries them. The reader may also be interested in U.S. Pat. Nos. 4,817,653, 5,293,887, and 4,828,059, also generally within the field.
In U.S. Pat. No. 4,971,591, Raviv and Davidovitz propose a "vehicle with vacuum traction" which facilitates the sliding of a vacuum cup along a surface, while the vacuum is supporting a certain amount of weight, either by using a low surface friction material in the vacuum cup itself, particularly the rim portion, or by placing a flexible sheet of low surface friction material under the cup. One cannot rely on the low surface friction of such a material for long, however, under industrial use conditions. See also the device of Lange and Kerr described in U.S. Pat. No. 5,890,250. They use a "grabber/slider vacuum cup" in a cleaning system which sprays cleaning and rinsing liquids on the surface. Wolfe et al, in U.S. Pat. No. 5,429,009, coordinate the movement and activation of several vacuum cups to manipulate a robot on a surface.
Such prior art machines and devices are generally not very effective on rough or slimy surfaces. The art is in need of a reliable, versatile robot capable of performing various tasks on inhospitable and steeply inclined surfaces.